EXCHANGE 


8061  '12  KVP  IVd 


Diphenyl-beta-Naphthylmethyl  and 
the  Color  of  Free  Radicals. 

A  Contribution  to  the  Chemistry  of 
Free  Radicals 


A  DISSERTATION 


row 


T.Q: 


SUBMITTED  IN   PARTIAL  FULFILLMENT   OF  THE  REQUIREMENTS 

FOR    THE  DEGREE  OF   DOCTOR  OF  PHILOSOPHY  IN  THE 

UNIVERSITY  OF  MICHIGAN 


-By 

Frederick  William  Sullivan',  Jr. 


EASTON,  PA. 

ESCHENBACH  PRINTING  COMPANY 
1921 


Diphenyl-beta-Naphthylmethyl  and 
the  Color  of  Free  Radicals. 

A  Contribution  to  the  Chemistry  of 
Free  Radicals 


A  DISSERTATION 


SUBMITTED  IN   PARTIAL  FULFILLMENT   OF  THE  REQUIREMENTS 

FOR   THE  DEGREE  OF  DOCTOR  OF  PHILOSOPHY  IN  THE 

UNIVERSITY  OF  MICHIGAN 


By 

Frederick  William  Sullivan,  Jr, 


EASTON,  PA. 

ESCHENBACH  PRINTING  COMPANY 
1921 


KXCHANGfc 


TABLE  OF  CONTENTS 


I    Introduction 1 

II  Experimental 4 

Diphenyl-/3-naphthyl  Carbinol . .  . 4 

Diphenyl-/3-naphthylmethane 5 

Preparation  of  Diphenyl-/3-naphthylmethyl 6 

Reaction  with  Oxygen 7 

Peroxide 8 

Action  of  Light  and  of  Acids 8 

Action  of  Iodine 8 

The  Conductivity 8 

Molecular  Weight 11 

Colorimeter  for  the  Study  of  the  Changes  in  Intensity  of  Color  of  Solutions  of 

Free  Radicals 16 

The  Effect  of  Dilution  on  the  Color  of  Solutions  of  Free  Radical  in  Benzene, 

Nitrobenzene  and  Cyclohexane  at  their  Respective  Freezing  Points 18 

The  Effect  of  Temperature  on  the  Color  of  Solutions  of  the  Free  Radical  in 

Carbon  Tetrachloride  and  in  Toluene 18 

III  Discussion  of  Results 19 

IV  Summary 23 


ACKNOWLEDGMENT 

It  is  a  pleasant  duty  to  express  my  sincere  appreciation  of  the  inspiring 
supervision  and  interest  of  Professor  M.  Gomberg,  at  whose  suggestion 
and  under  whose  direction  this  work  was  carried  out. 

FREDERICK  WIUJAM  SULLIVAN,  JR. 
Ann  Arbor,  Mich. 
August  23,  1922 


DIPHENYL-BETA-NAPHTHYL-METHYL    AND    THE   COLOR   OF 

FREE  RADICALS 

Our  purpose  in  the  present  investigation  has  been  to  prepare  the  free 
radical,  diphenyl-/3-naphthylmethyl 


and  to  study  it  with  regard  to  the  characteristic  chemical  reactions  and 
physical  properties  of  free  radicals ;  as  a  later  development,  because  of  the 
pecular  adaptability  of  this  radical  to  the  problem,  it  was  studied  es- 
pecially from  the  standpoint  of  the  relation  between  color  and  chemical 
constitution.  The  characteristic  phenomena  investigated  included  the 
absorption  of  oxygen,  the  reaction  with  iodine,  the  effects  produced  by 
light  and  acids,  the  conductivity,  the  dissociation  of  the  hexa-aryl  ethane, 
the  formation  of  additive  compounds,  and  finally,  the  effect  of  dilution 
and  temperature  changes  upon  the  color  of  solutions  of  the  free  radical. 

The  striking  fact  that  triphenyl methyl,  although  a  hydrocarbon,  is 
colored  when  in  solution  has  given  rise  to  many  explanations  in  order  to 
account  for  this  phenomenon.  The  principal  theories  regarding  the  re- 


lation   between  color  and  constitution  of  triphenylmethyl   are,   briefly 
stated,  the  following. 

1.  Colorless    hexaphenylethane    dissociates   to   form    the   colored    free    radical,1 

RsCCRj  — >  2  R3C-. 

2.  Dissociation  occurs  and  is  followed  by  tautomerization  of  the  benzerj 
phenylmethyl  into  the  quinonoid  monomolecular  tautomer.     The  color  is  attributed  to 
the  quinonoid  tautomer,  C.'-     (Cf.  p.   1832.) 

(C6H5)3C-C(C,H6)3  ±^  (C6H6)3C  +  (C6H5)3C 
A 


(C,H,),C  -v 

XTT. 

C 

The  work  on  p-halogen  substitution  products  of  triphenylmethyl  pro- 
vides definite,  strictly  chemical,  evidence  for  the  existence  of  tautomerism 
with  the  formation  of  some  kind  of  a  quininoid  tautomer.3 

The  evidence  based  on  purely  physical  chemical  considerations  is  some- 
what contradictory.  Schmidlin  observed  that  upon  shaking  a  solution 
of  triphenylmethyl  with  oxygen  the  color  vanishes  but  reappears  on  stand- 
ing, and  that  this  phenomenon  takes  place  several  times  before  the  solution 
is  completely  and  permanently  decolorized.  By  weighing  the  amount  of 
peroxide  formed  in  a  single  decolorization,  he  was  able  to  calculate  the 
amount  of  the  colored  form  which  was  present.  His  results  indicated  that 
the  ratio  of  colorless  to  colored  form  was  about  10  to  1.  However,  since 
the  molecular  weight  of  triphenylmethyl  at  room  temperature  corresponds 
to  the  dimolecular  formula,  Schmidlin  concluded  that  color  must  be  due 
to  tautomerism  and  not  dissociation. 

Schmidlin  also  observed  the  variation  in  the  intensity  of  color  of  tri- 
phenylmethyl solutions  at  different  temperatures  and  found  that  at  the 
freezing  point  of  chloroform,  — 63°,  the  color  entirely  disappeared.  Later4 
he  determined  the  molecular  weight  of  triphenylmethyl  in  benzene  in  an 
apparatus  devised  to  permit  the  determination  by  the  freezing-point  and 
boiling-point  methods  on  the  same  sample,  and  found  no  changes  in  dis- 
sociation at  the  different  temperatures.  He  then  conducted  colorimetric 
determinations  over  a  range  of  temperatures  from  the  freezing  point  to  the 
boiling  point  of  benzene  and  found  that  the  color  increased  6-fold.  From 
these  results  he  concluded  that  the  intensification  of  color  of  triphenyl- 

1  Baeyer,  Ber.,  35,   1195  (1902).     Flurscheim,  J.  prakt.   Chem.,  71,  505   (1905). 
Chichibabin,  Ber.,  40,  3970  (1907).     Wieland,  ibid.,  42,  3029  (1909).     Piccard,  Ann., 
381,  347  (1911). 

2  Gomberg,  Ber.,  46,  228  (1913). 

3Gomberg  and  others,  ibid.,  39,  3294  (1906);  ibid.,  40,  1886  (1907)-  Ann     370, 
181  (1909);  ibid.,  376,  208  (1910);  /.  Am.  Chem.  Soc.,  33,  538  (1911). 
4  Schmidlin,   Ber.,  45,  3181    (1912). 


methyl  solutions  with  rise  of  temperature  must  be  due  to  something  other 
than  dissociation. 

On  the  other  hand,  Wieland,  Schlenk  and  Mair,  and  Piccard  took  the 
very  opposite  point  of  view.  Wieland5  concluded  from  Schmidlin's 
earlier  experiments  and  from  -the  molecular  weight  determinations  of 
Gomberg  and  Cone  that,  after  allowing  for  the  inherent  errors  of  the  cryo- 
scopic  method,  the  dissociation  hypothesis  completely  explains  color  forma- 
tion. 

Schlenk  and  Mair6  gave  as  evidence  that  the  increase  of  color  with  rising 
temperature  is  due  to  dissociation,  the  results  of  their  molecular  weight 
determinations  on  triphenylmethyl  by  the  boiling-point  method.  They 
found,  contrary  to  Schmidlin,  that  hexaphenylethane  in  boiling  benzene 
is  dissociated  to  the  extent  of  25%.  Hence,  according  to  them  the  increase 
in  color  intensity  is  due  to  dissociation. 

What  seemed  to  be  the  most  convincing  evidence  in  favor  of  the  dis- 
sociation theory  is  found  in  the  work  of  Piccard7  on  the  increase  of  color 
of  triphenylmethyl  solutions  with  dilution.  This  behavior  constitutes  a 
deviation  from  Beer's  law,  which  states  that  the  color  absorption  of  so- 
lutions should  remain  constant  if  there  were  no  chemical  changes  on  di- 
lution. In  the  case  of  hexaphenylethane  we  are  concerned  with  one  of  two 
phenomena,  either  tautomerism  or  dissociation.  If  it  were  tautomerism 
the  equilibrium  would  be  between  two  isomers  and,  Piccard  assumes,  such 
an  equilibrium  should  be  independent  of  dilution ;  but  if  it  were  dissoci- 
ation then  the  equilibrium  would  be  between  a  polymer  and  the  products 
of  its  dissociation,  and  such  an  equilibrium  should  be  influenced  by  dilution. 
He  conducted  a  series  of  experiments  on  hexaphenylethane  solutions  and 
found  a  decided  increase  in  color  upon  dilution.  He  therefore  concluded 
that  the  phenomenon  must  be  dissociation. 

Although  Piccard's  assumption  is  in  accordance  with  the  general  belief8 
that  the  equilibrium  between  tautomers  is  independent  of  dilution  there 
is  much  experimental  evidence  to  the  contrary.  W.  Wislicenus9  found 
that  the  equilibrium  between  the  aldo  and  enol  forms  of  ethyl  formyl 
phenyl  acetate  was  shifted  in  favor  of  the  enol  form  by  concentration.  Kurt 
H.  Meyer  and  Kappelmeier10  found  that  the  equilibrium  between  the  enol 
and  keto  forms  of  aceto-acetic  ester  in  hexane  varied  from  a  concentration 
of  9.3%  enol  in  a  90%  solution  of  the  ester  to  58.6%  in  a  2%  solution. 

5  Wieland,  Ref.  2. 

t;  Schlenk  and  Mair,  Ann.,  394,  178  (1912). 

7  Piccard,  ibid.,  381, 347  (1911);  Arch.  sci.  phys.  Nat.,  Geneva,  1913,  368.    Hantzsch 
Ann.,  384,  135  (1911);  ibid.,  398,  379  (1913). 

8  Ostwald,  "Lehrbuch  der  Allgemeine  Chemie,"  Wilhelm  Englemann  2nd  ed.,  1902, 
p.  604. 

9  Wislicenus,  Ann.,  291,    147   (1896). 

"'  Meyer  and  Kappelmeier,  Ber.,  44,  2722  (1911). 


More  recently,  O.  Miller11  studied  the  equilibrium  between  the  two  forms 
of  2-amino-a-naphthoquinone-imide  and  found  that  this  equilibrium  was 
influenced  by  dilution. 

O  O 

^  [NH2 


IH 

So  it  seems,  after  all,  that  Piccard's  results  do  not  prove  that  color 
in  triphenylmethyl  solutions  is  necessarily  due  to  dissociation,  and  the 
possibility  remains  that  it  may  be  due  to  tautomerism,  or  perhaps  to 
dissociation  with  subsequent  tautomerism. 

The  difficulties  in  the  study  of  this  question  and  the  contradictory 
nature  of  the  conclusions  results  from  the  fact  that  hexaphenylethane  is 
very  slightly  dissociated,  not  more  than  5%  at  ordinary  temperatures,  and 
therefore  conclusions  regarding  the  relation  between  color  and  dissoci- 
ation must  be  based  largely  on  speculation.  Its  color  is  neither  sufficiently 
intense  nor  sufficiently  different  from  that  of  its  decomposition  products 
for  reliable  colorimetric  study.  In  diphenyl-/3-naphthylmethyl  we  have 
a  substance  of  very  considerable  and  accurately  measurable  dissociation; 
its  color,  bright  red  in  concentrated  solutions  shading  to  light  yellow  in 
dilute  solutions,  lends  itself  readily  to  colorimetric  study;  it  is  quite 
stable  towards  light;  it  is  readily  soluble  in  a  variety  of  solvents  throughout 
a  wide  range  of  temperature.  In  addition,  it  shows  striking  diminution  of 
color  within  the  temperature  range  of  ordinary  cryoscopic  determinations. 
On  account  of  this  fortuitous  combination  of  properties,  a  study  of  diphenyl- 
j3-naphthylmethyl  was  undertaken  in  an  effort  to  throw  some  light  on  the 
relation  between  color  formation  and  changes  in  concentration  and  in 
temperature. 

Experimental 


Diphenyl-/3-naphthyl  Carbinol,  (CeHBM/S-CioI^COH.—  Diphenyl-/3-naphthyl  car- 
binol  was  prepared  by  the  Grignard  reaction  from  ethyl  /S-naphthoate  and  phenyl- 
magnesium  bromide.  Experiments  showed  this  method  to  be  preferable  to  the  prepara- 
tion from  /3-naphthylphenyl  ketone  and  bromobenzene,  or  from  benzophenone  and 
/3-bromonaphthalene.  The  starting  substance  in  the  preparation  was  the  sodium  salt  of 
/3-naphthalene  sulfonic  acid  which  was  converted  to  the  nitrile  by  dry  distillation  with 
potassium  ferrocyanide.12  Two  pares  of  the  sulfonate  and  one  part  of  anhydrous  ferro- 
cyanide  were  heated  in  250g.  portions  in  Pyrex  Kjeldahl  flasks  placed  horizontally  in  an 
air-bath  so  that  the  vapors  were  removed  as  fast  as  formed.  The  condensate  was  dried 
by  heating  until  the  water  was  driven  off  and  was  then  distilled.  The  portion  boiling 
between  290°  and  310°  was  collected.  The  nitrile  can  be  crystallized  from  petroleum 

11  Miller,  /.  Russ.  Phys.  Chem.  Soc.,  47,  1544  (1915). 

12  Eckstrand,  /.  prakt.  Chem.,  38,  139  (1888). 


ether  and  melts  at  68°.  The  redistilled  substance  was  hydrolyzed  according  to  the  pro- 
cedure of  Baeyer  and  Besemfelder13  and  the  resulting  acid  purified  by  dissolving  in  alkali 
and  reprecipitating  with  acid.  In  this  manner  650  g.  of  acid  was  prepared  from  3900  g. 
of  the  sulfonate,  a  yield  of  20%. 

For  the  esterification  of  the  acid,  20  g.  of  /3-naphthoic  acid,  20  g.  of  sulfuric  acid  and 
200  cc.  of  absolute  alcohol  were  boiled  under  a  reflux  condenser.  The  reaction  product 
was  poured  into  an  excess  of  dil.  alkali,  the  ester  was  extracted  from  this  mixture,  dried 
and  distilled,  and  the  fraction  between  300°  and  304°  was  collected.  The  yield  of  ester 
was  97.5%.  When  the  proportions  were  changed  to  1  part  of  0-naphthoic  acid,  1  part 
of  sulfuric  acid,  and  2  parts,  instead  of  10,  of  alcohol,  the  yield  of  the  ester  was 
reduced,  but,  since  the  unchanged  acid  could  be  recovered,  this  latter  method  was 
adopted. 

Ullmann14  found  that  the  product  of  the  reaction  between  methyl-/3-naphthoat,e 
and  phenylmagnesium  bromide  was  an  oil  and  he  was  unable  to  isolate  the  carbinol  from 
it.  Following  the  same  procedure  and  using  either  the  methyl  or  ethyl  ester  we  were 
able  to  obtain  the  crystalline  carbinol  but  the  yield  was  not  more  than  25%.  The 
yield  was  improved  by  replacing  the  ether  after  the  formation  of  the  Grignard  reagent  by 
benzene  or,  better,  by  toluene.  Xylene  was  not  so  satisfactory.  The  following  pro- 
cedure was  finally  adopted.  A  mixture  of  10  g.  of  magnesium  turnings  in  50  cc.  of 
bromobenzene  and  200  cc.  of  ether  was  boiled  until  the  metal  disappeared;  100  cc.  of 
toluene  was  then  added  and  the  ether  was  distilled ;  28  g.  of  ethyl  /3-naphthoate  was  then 
added  gradually;  the  heat  of  the  reaction  kept  the  toluene  boiling,  and  the  temperature  of 
the  reaction  mixture  was  about  115°.  After  the  ester  had  been  added  and  when  boiling 
had  ceased,  the  mixture  was  cooled  and  decomposed  with  ice  and  acetic  acid.  The 
product  was  distilled  with  steam  and  the  residue  was  taken  up  in  carbon  disulfide.  The 
solution  was  dried,  filtered  and  concentrated.  On  the  addition  of  petroleum  ether,  a 
light-yellow  crystalline  product,  the  carbinol,  separated  and  this  was  suitable  for  con- 
version to  the  chloride  without  further  purification;  yield,  28  g.,  or  65%.  The  car- 
binol is  readily  soluble  in  all  the  usual  solvents  and  can  be  recrystallized  from  alcohol  or, 
better,  from  carbon  disulfide,  by  the  addition  of  petroleum  ether.  The  pure,  white, 
recrystallized  product  melts  at  117.5°. 

Analyses.  Calc.  for  C23H18O:  C,  89.0;  H,  5.84.  Found:  C,  89.4,  89.4;  H,  5.90, 
5.92. 

When  boiled  with  acetic  acid  in  the  presence  of  mineral  acids,  the  carbinol  is  con- 
verted to  the  fluorene. 

(C6H6)2(C10H7)COH  >    |  6     '  NCH.C6H8.  +  H2O 

C10H/ 

This  substance,  when  recrystallized  from  chloroform  by  the  addition  of  alcohol,  melts 
at  137°  and  agrees  in  all  properties  with  the  substance  described  by  Ullmann. 

Diphenyl-j3-naphthylmethane,  (C6H6)2(/3-C10H7)CH. — Ten  g.  of  the  carbinol  is 
dissolved  in  200  cc.  of  acetic  acid  and  the  solution  is  boiled  with  20  g.  of  zinc  dust  until 
a  drop  no  longer  gives  a  red  color  with  sulfuric  acid.  The  acetic  acid  solution  is  poured 
into  water  and  partly  neutralized.  The  ether  extract  is  washed  with  alkali,  dried  and 
concentrated.  The  hydrocarbon  crystallizes  on  the  addition  of  alcohol;  yield,  9  g.,  or 
95%;  m.  p.,  77-78°. 

Analysis.  Calc.  for  CZ3U, 8:  C,  93.83;  H,  6.17.  Found:  C,  93.44;  H,  6.33.  Mol. 
wt.  Calc.:  294.  Found:  293. 


13  Baeyer  and  Besemfelder,  Ann.,  266,  188  (1891). 

14  Ullmann,  Ber.,  38,  2218  (1905). 


6 

The  properties  of  diphenyl-/3-naphthylmethane  as  here  described  differ  from  those  which 
appear  in  the  chemical  literature  and  which  are  based  on  the  work  of  Lehne.15 

Diphenyl-/3-naphthylmethyl  Chloride,  fC6Hfi)2(i3-C,oH7)CCl.— The  chloride  is 
prepared  by  saturating  an  ether  solution  of  the  carbinol  with  hydrogen  chloride  in  the 
presence  of  calcium  chloride.  After  standing,  the  solution  is  decanted,  boneblack 
is  added  and  the  ether  is  evaporated.  The  oily  residue  is  taken  up  in  low-boiling  petro- 
leum ether,  filtered  and  allowed  to  crystallize.  The  recrystallized  substance  melts  at 
94.5°,  and  the  yield  is  practically  quantitative.  The  use  of  acetyl  chloride  instead  of 
hydrogen  chloride  in  this  preparation  leads  to  the  formation  of  colored  impurities,  and  is 
not  recommended. 

Analysis.     Calc.  for  C«H17C1:    Cl,  10.79.     Found:    10.71. 

The  chloride  gives  red  additive  compounds  with  stannic  and  mercuric  chlorides. 
When  dissolved  in  alcohol  or,  preferably,  in  an  alcoholic  solution  of  sodium  ethylate, 
the  chloride  is  converted  to  diphenyl-£-naphthylmethyl  ethyl  ether,  (C6H5)2(/3-CioH7)- 
COC2Hj,  a  colorless  crystalline  substance  which  melts  at  114°.  The  chloride  gives  an 
anilide,  (C«H5)2(0-CIOH7).C.NH.C6H6,  melting  at  158.5°. 

Diphenyl-j3-naphthylmethyl  Bromide,  (C6H5)2(i3-CioH7)CBr.-— The  bromide  can  be 
prepared  by  the  addition  of  acetyl  bromide  to  a  benzene  solution  of  the  carbinol.  After 
recrystallizing  from  petroleum  ether  it  is  colorless  and  melts  at  136°.  On  long  standing 
it  turns  red  with  the  evolution  of  acid  fumes. 

Analysis.     Calc.  for  C23H17Br:   Br,  21.4.     Found:   21.6. 

Preparation  of  Diphenyl-0-naphthylmethyl. — Five  g.  of  diphenyl- 
0-naphthylmethyl  chloride  and  5  g.  of  molecular  silver  are  placed  in  a  test- 
tube  and  35  cc.  of  carbon  disulfide  is  added.  The  tube  is  then  corked, 
taking  all  the  necessary  precautions,  and  shaken  for  several  hours.16'17 
When  the  reaction  is  complete,  the  bright  red  solution  is  siphoned  into  the 
free-radical  apparatus.  The  apparatus  is  immersed  in  warm  water,  suc- 
tion is  applied  and  the  solvent  is  completely  evaporated.  Five  cc.  of 
acetone  is  added,  the  oily  residue  is  dissolved  and  the  apparatus  is  filled 
with  carbon  dioxide.  The  solution  is  cooled  to  a  temperature  below  0°; 
crystals  of  the  free  radical  separate  after  standing  for  2  to  3  days.  The 
solvent  is  drawn  off  and  the  crystals  washed  with  acetone,  then  dried 
under  reduced  pressure  in  a  stream  of  carbon  dioxide ;  2 . 5  to  3  g.  of  pure 
white  or  light  yellow,  finely  divided,  crystalline  powder,  the  triarylmethyl, 
is  thus  obtained.  The  compound  is  very  soluble  in  all  the  usual  solvents 
except  petroleum  ether.  It  melts  in  an  atmosphere  of  carbon  dioxade 
between  135°  and  140°  to  a  reddish  liquid.  The  dry  substance  is  quite 
stable  at  ordinary  temperatures  and  may  be  exposed  to  air  for  short  periods 
without  danger  of  oxidation. 

Calc.  for  C23H17:C,  94.16;  H,  5.84.     Found:  C,  93.92;  H,  6.02. 

Formation  of  Additive  Compounds  with  Solvents. — Owing  to  its 
extreme  solubility,  it  is  very  difficult  to  crystallize  diphenyl-/3-naphthyl- 
methyl  and  the  crystallization  always  requires  from  2  to  3  days.  The 

15  Lehne,  Ber.,  13,  358  (1880). 

16  Gomberg  and  Schoepfle,  J.  Am.  Chem.  Soc.,  39,  1659  (1917). 

17  Gomberg   and    Cone,    Ber.,   37,   2034    (1904). 


ketones  are,  as  a  class,  best  suited  as  solvents  for  recrystallization,  although 
it  is  possible  to  recrystallize  the  free  radical  from  a  few  solvents  of  other 
classes.  In  order  to  determine  whether  additive  compounds  were  formed 
with  different  solvents,  the  procedure  already  given  for  the  recrystalliza- 
tion of  the  substance  from  acetone  was  used  with  the  substitution  in  each 
case  of  the  solvent  whose  additive  tendency  was  to  be  investigated.  In 
case  the  solvent  was  one  of  high  boiling  point,  the  free  radical  after  re- 
crystallization  was  freed  from  the  non-volatile  solvent  by  washing  with 
a  little  low-boiling  petroleum  ether.  The  solid  substance  was  dried  thor- 
oughly under  reduced  pressure  at  room  temperature.  A  weighed  sample 
of  the  dry  free  radical  was  then  placed  in  a  porcelain  boat  and  heated  at 
70°  under  reduced  pressure  in  an  atmosphere  of  carbon  dioxide.  The  free 
radical  was  recrystallized  from  the  following  solvents  and  separated  without 
solvent  of  crystallization:  (I)  ketones:  acetone,  methylethyl  ketone, 
methylhexyl  ketone,  dipropyl  ketone;  (II)  ethers:  diethyl  ether,  ethyl 
250-amyl  ether;  (III)  esters:  ethyl  acetate. 

With  methylbutyl  ketone,  diphenyl-/3-naphthylmethyl  gives  an  addi- 
tive compound  in  which  the  proportion  of  ketone  to  free  radical  approaches 
that  required  in  accordance  with  the  general  formula  of  such  compounds 
with  triphenylmethyl,  R3C— CR3.C6Hi2O.  Three  samples,  1.020,  1.526 
and  0 . 481  g.  showed  0 . 073,  0 . 175  and  0 . 050  g.  loss  or  7 . 1,  1 1 . 8  and  10 . 4%, 
respectively,  whereas  the  calculated  loss  is  14.6%. 

Among  other  solvents  which  were  tried  but  from  which  the  free  radical 
failed  to  crystallize  altogether  were  benzene,  benzonitrile,  caprylene  and 
cyclohexane. 

Reaction  with  Oxygen. — Diphenyl-/3-naphthylmethyl  rapidly  com- 
bines with  the  amount  of  oxygen  necessary  for  the  formation  of  the  peroxide 
in  accordance  with  the  equation,  2(C23Hi7)  +  O2 — >(C23Hi7)O-O(C23Hi7). 
The  apparatus  for  the  measurement  of  the  oxygen  absorption18  consists 
of  an  absorption  bottle  which  is  connected  by  a  heavy  rubber  tube  to  a  gas 
buret.  To  determine  the  oxygen  absorption,  a  weighed  quantity  of  di- 
phenyl-/3-naphthylmethyl  chloride  and  an  equal  weight  of  silver  were 
placed  in  a  tube,  bromobenzene  was  added  and  the  tube  was  sealed  and 
shaken  for  several  hours.  The  tube  containing  the  reaction  mixture  was 
placed  in  bromobenzene  in  the  absorption  bottle,  the  apparatus  was  sealed, 
exhausted  and  filled  with  oxygen.  When  the  system  had  come  to  equi- 
librium, the  tube  was  broken  by  shaking  the  bottle.  Shaking  was  con- 
tinued until  the  color  of  the  free  radical  had  permanently  disappeared 
and  the  reading  was  taken  half  an  hour  later.  The  oxygen  absorbed 
by  the  previously  isolated,  crystalline,  free  radical  was  also  determined 
and,  of  course,  silver  was  left  out.  The  following  table  gives  the  results 
of  typical  experiments. 

18  Ref.  17,  p.  1661. 


8 

TABUJ! 

REACTION  WITH  OXYGEN 
Weight  of  sample  Oxygen  absorption 

C23H17C1  C2sH17  Cc.  at  Stand.  Cond.  %  of  Calc. 
G.                              G. 

1  1.200  ...  40.8  99.6 

2  1.200  ...  41.6  102 

3  1.200  ...  41.0  100 

4  ...  1.029  39.3  100 

5  ...  1.000  39.0  102 

Peroxide. — The  yield  of  peroxide  varies  greatly  under  different  con- 
ditions. When  an  ether  solution  of  the  free  radical  is  oxidized  with  air 
the  yield  is  72%,  while  the  use  of  benzene  as  a  solvent  reduces  the  yield 
to  46%.  The  peroxide  when  recrystallized  from  benzene  is  pure  white 
and  melts  at  166°. 

Analyses.     Calc.  for  C48H34O2:    C,  89.3;  H,  5.54.     Found:    C,  89.3,  89.6;  H,  5.54, 
5.50. 

Action  of  Light  and  of  Acids. — The  free  radical  is  not  very  sensitive  to 
light.  A  5%  solution  in  bromobenzene  which  was  exposed  to  full  day- 
light during  three  days  in  December  still  absorbed  75%  of  the  calculated 
amount  of  oxygen.  When  a  10%  solution  of  the  free  radical  in  bromo- 
benzene was  treated  with  an  equal  volume  of  bromobenzene  saturated  with 
hydrogen  chloride,  the  color  of  the  free  radical  rapidly  disappeared  and  the 
solution,  after  3  hours,  absorbed  no  oxygen.19 

Action  of  Iodine. — Diphenyl-jS-naphthylmethyl  reacts  with  iodine  in 
accordance  with  the  following  equation,  2(C6H5)2(/3  Ci0H7)C  +  1% — > 
2(C6H5)2(/3-CioH5)CI  but  an  equilibrium  is  reached  before  the  reaction 
has  gone  to  completion.  A  weighed  sample  of  the  free  radical  in  benzene 
was  titrated  with  a  0. 1  Absolution  of  iodine  in  benzene.  The  color  of  the 
iodine  disappeared  rapidly  until  70%  of  the  calculated  amount  was  added, 
then  the  absorption  of  iodine  ceased.  The  change  from  the  color  of  the 
free  radical  to  the  color  produced  by  excess  of  iodine  can  be  readily  de- 
tected. Three  samples  of  1.000  g.  each  required  23.0,  23.7  and  25.0  cc. 
of  0 . 1  N  iodine  solution,  or  67 . 5,  70 . 0  and  73 . 5%  of  the  calculated  amount, 
respectively. 

The  presence  of  the  iodide  in  solution  was  demonstrated  by  its  conver- 
sion to  the  anilide,  which  substance  proved  to  be  identical  with  diphenyl- 
/3-naphthylmethyl  anilide  prepared  from  the  corresponding  chloride. 

The  Conductivity. — For  the  determination  of  the  conductivity  a  cell 
resembling  the  one  used  in  the  earlier  work20  was  used.  It  differed  from 
the  other  in  that  the  electrodes  were  placed  horizontally  instead  of  verti- 
cally. The  cell  constant  was  determined  using  a  0.02  N  potassium 

19  Ref.  17,  p.  1663. 

20  Gomberg    and    Cone,    Ber.,    38,    1342    (1905). 


9 

chloride  solution  at  25°.  The  sulfur  dioxide  was  passed  through  a  tube 
of  phosphorus  pentoxide  50  cm.  long,  and  was  then  condensed  in  the  cell, 
which  was  surrounded  by  a  freezing  mixture.  The  cell  was  then  stoppered 
and  placed  in  a  Dewar  flask  which  contained  liquid  sulfur  dioxide.  By 
such  a  procedure  it  was  possible  to  maintain  in  the  surrounding  bath  a 
constant  temperature  of  —  8°,  the  boiling  point  of  liquid  sulfur  dioxide. 
It  was  found  that  the  cell  could  be  removed  from  the  cooling  solution 
long  enough  to  weigh  it  without  generating  too  much  pressure.  After 
weighing,  the  cell  was  connected  into  the  usual  Wheatstone  bridge  appa- 
ratus, and  the  conductivity  of  the  pure  solvent  was  determined.  In 
all  experiments,  the  conductivity  of  the  solvent  was  between  10  ~5  and  10~8 
mhos.  The  material  whose  conductivity  was  to  be  determined  was  intro- 
duced in  3  portions.  The  cell  was  shaken  after  each  addition  until  all 
the  substance  was  dissolved,  as  indicated  by  the  fact  that  the  reading  had 
become  constant.  Determinations  were  made  of  the  conductivity  of 
triphenylmethyl  and  of  its  chloride  and  bromide  at  —  8°,  with  the  cell 
immersed  in  liquid  sulfur  dioxide,  and  at  0  °  in  a  mixture  of  ice  and  water. 
The  conductivities  of  diphenyl-a-naphthylmethyl  chloride  and  bromide, 
and  those  of  diphenyl-0-naphthylmethyl  chloride  and  bromide  were  de- 
termined at  —  8°  only. 

Contrasting  with  its  behavior  in  other  solvents,  diphenyl-/3-naphthyl- 
methyl  was  found  to  be  quite  insoluble  in  sulfur  dioxide.  For  this  reason 
the  substance  was  dissolved  in  toluene  and  measured  quantities  of  this 
solution  were  added  to  sulfur  dioxide.  The  same  procedure  was  carried 
out  with  triphenylmethyl  and  it  was  found  that  in  both  cases  the  re- 


II 

CONDUCTIVITIES  IN  SULFUR  DIOXIDE 

(C6H6)3CC1  (C6H*)3CBr  (C6H5)2(a  C10H7)-    (C6H5)2(«-C10H7)- 

CC1  CBr 


M-8       Mo              M-g 

Mo                 M-g 

V 

M-, 

1   154 

24. 

2   20. 

2 

237 

113 

118    2600    128 

1180 

138 

2   43 

.7  14. 

0   11. 

3 

112 

108 

112    179    70 

223 

118 

3   18 

.2   9. 

1    7. 

8 

39.6 

97 

.6 

99.5    59.4   50 

55.7 

102 

1  205 

27. 

9   23. 

1 

189 

117 

122    1271    117 

683 

124 

2   61 

.0  16. 

6   13. 

4 

60.7 

105 

107    334    84.6 

184 

108 

3   26 

.3  11. 

5    9. 

2 

28.2 

96 

,4 

97.9    46.9   44.8 

46.7 

95.6 

(C,H5)3C-  in  SO2 
+  C7H8 

V      M-g  %  CyHs  by 

Vol 

(C.H,),(0-CioH7)C-     (C«H.)i(0-Cio-   (C6H6 
in  SO2  +  C7H8         H7)CC1       H7 
.  V      /*_g  %  C7H8  by  Vol.   V       p_8    V 

)CBr 

M-g 

1 

211 

31.4 

2.62 

227 

34 

2.57    1072    73 

.8  692 

131 

2 

108 

26.3 

5.11 

116 

27. 

1 

5.02    212    41 

.4  148 

110 

3 

57 

20.2 

9.72 

60.2 

22. 

0 

9.57     30.5  20 

.1   25.9 

96 

.5 

1 

195 

28.6 

2.81 

261 

39 

,4 

2.24     

.   892 

129 

2 

100 

26.6 

5.47 

133 

31 

4 

4.39    283    42 

.2  325 

123 

3 

52.9 

19.5 

10.4 

68.4 

22. 

5 

8.41     27.1  23 

.2   27.4 

96 

.6 

10 

suiting  solutions  of  the  mixed  solvents  were  good  conductors,  much  better 
than  a  solution  of  triphenylmethyl  in  sulfur  dioxide  alone.  The  readings 
were  taken  1  hour  after  the  additions  were  made.  The  accompanying 
tables  and  curves  show  the  results  of  these  experiments. 


L/TERS 


Conductivity  in  Hydrocyanic  Acid.  —  The  same  apparatus  was  used  as 
in  the  determination  of  the  conductivities  in  sulfur  dioxide.  The  hydro- 
cyanic acid  was  generated  by  the  addition  of  a  concentrated  solution  of 
sodium  cyanide  to  a  50%  solution  of  sulfuric  acid  and  the  gas  evolved 
was  dried  by  calcium  chloride  and  phosphorus  pentoxide.  It  was  then 
condensed  in  the  conductivity  cell.  The  specific  conductivity  of  the  hydro- 
cyanic acid  was  never  greater  than  10~5  mhos. 

It  was  found  that  the  conductivity  of  the  triarylmethyl  halides  in  hydro- 
cyanic acid  did  not  remain  constant,  but  changed  gradually.  For  this 
reason  it  was  not  possible  to  determine  the  conductivity  by  dissolving 
the  solid  substance  in  this  solvent.  Experiments  showed  that  the  con- 
ductivity of  triphenylchloromethane  in  hydrocyanic  acid  to  which  15% 
of  benzene  was  added,  was  not  greatly  affected  by  the  further  addition  of 
benzene  up  to  20%.  It  was  found  that  benzene  and  hydrocyanic  acid 
mixed  without  a  change  in  volume.  It  was,  therefore,  decided  to  add  the 
halides  dissolved  in  benzene  to  hydrocyanic  acid;  22  cc.  of  the  solvent 
was  condensed  in  the  cell  and  3  cc.  of  benzene  was  added.  To  this  mixture 
was  added,  first,  0  .  07  cc.  of  benzene  containing  the  substance  whose  con- 
ductivity was  to  be  determined,  second,  0  .  23  cc.  more  and,  finally,  0  .  7 


11 


cc.,  a  total  of  1  cc.  of  solution.  The  readings  were  taken  5  minutes  after 
each  addition  and  the  series  of  three  readings  was  always  completed  in  15 
minutes.  The  conductivities  were  all  determined  at  0°  using  an  ice-bath. 
The  density  of  hydrocyanic  acid  at  this  temperature  is  0.7112. 


III 

CONDUCTIVITY  IN  HYDROCYANIC  ACID 


(C6H5)3CC1 


(«-C10H7)(C6H6)2CCl 
V  «. 


1659 
391 
121 

1668 
393 
121 


111 
77 
44 

115 
75 
45 


211 
206 
166 
212 
202 
165 


1794 
422 
130 

1704 
424 
131 


161 
117 

77 
170 
118 

76 


(/3-C10H7)(C6H6)2CBr 
V  »«„ 


(C6H5)3CBr 

V  i 

1790 

420 

130 
1726 

406 

125 

(/3-C1oH7)(C6H6)2CCl 

V  Mo 

166 
125 

86 

166  • 
122 

85 

The  conductivities  of  the  chlorides  and  bromides  of  triphenylmethyl, 
diphenyl-a-naphthylmethyl  and  diphenyl-/3-naphthylmethyl  were  de- 
termined in  hydrocyanic  acid.  Unfortunately  the  conductivities  of  the 
free  radicals  themselves  could  riot  be  determined  because  when  a  benzene 
solution  of  a  free  radical  is  added  to  hydrocyanic  acid  an  amorphous 
precipitate  is  formed  and  the  solvent  remains  colorless  and  nonconducting. 


(a-C10H7)(C6H6)2CBr 

V  Mo 

1830  200 

416  197 

129  174 

1740  192 

409  198 

126  174 


1690 
404 
125 

1711 
404 
125 


1767 
382 
127 

1704 
401 
124 


216 
203 
191 
193 
206 
191 


2. 

Cououcr/v/r  r  /v 


Z  /  TERS  COA/7%/MWG/  Mot  ECUL  A/?  Wr  V 

Molecular  Weight. — The   molecular  weight  of  dipheny-/3-naphthyl- 

methyl  was  determined  in  8  solvents,  covering  a  temperature  range  of 


12 


from  — 22°  to  80°.  The  standard  Beckmann  apparatus  with  electromag- 
netic stirrer  was  used.  Details  for  the  manipulation  for  solvents  freezing 
above  0°  have  been  previously  published.21  The  determination  of  the 
molecular  weight  in  solvents  freezing  at  low  temperatures  is  described 
below.  A  large  number  of  solvents  were  tried  out,  including  benzonitrile, 
dimethyl  resorcin,  ethylene  chlorohydrin  and  <?-nitrotoluene  but  all  these 
were  discarded  because  of  supercooling;  aniline  was  found  unsuitable 
because  of  the  insolubility  of  the  free  radical  in  it.  The  solvents  finally 
chosen  were  carbon  tetrachloride,  m.  p.  — 22°,  and  ethylene  chlorobromide 
whose  freezing  point,  — 17°,  had  been  determined  by  Schneider.22 

The  apparatus  used  consisted  of  the  usual  freezing-point  tube  which 
was  passed  through  a  rubber  stopper  into  a  Dewar  flask  in  which  ether 
could  be  evaporated  under  reduced  pressure,  and  this  served  as  the  bath. 
A  thermometer,  a  tube  leading  to  the  suction  pump  and  a  tube  for  the  in- 
troduction of  ether  were  also  passed  through  the  same  stopper.  A  de- 
scription of  the  procedure  for  the  determination  of  the  cryoscopic  con- 
stant of  carbon  tetrachloride  will  give  a  typical  illustration  of  the  use  of  the 
apparatus. 

The  freezing-point  tube  containing  the  thermometer,  stirrer  and  a  weighed  quantity 
of  solvent  was  placed  in  the  Dewar  flask.  Ether  was  introduced  into  the  latter  until 
the  lower  portion  of  the  tube  was  immersed. 
The  stirrer  was  then  set  in  motion  and  suction 
was  applied.  The  rapid  evaporation  of  the 
ether  surrounding  the  freezing-point  tube  re- 
duced the  temperature,  and  freezing  occurred 
with  very  little  supercooling.  After  each  read- 
ing the  crystals  were  melted,  and  five  readings 
were  taken  for  each  freezing  point.  Three  ad- 
ditions of  the  solute  were  made.  Duplicate 
determinations  of  the  constant  were  made  with 
triphenylmethane  and  benzophenone  as  the 
solutes. 

As  will  be  seen  from  the  accompany- 
ing curve,  when  this  procedure  was  fol- 
lowed the  value  of  the  so-called  freezing- 


//V  DfGRftt   C. 


point  constant  varied  with  the  depression  in  carbon  tetrachloride.  For 
this  reason  it  was  thought  advisable  to  use  the  values  obtained  from 
this  curve  for  K  when  calculating  the  molecular  weight  of  the  free  radical. 
Beckmann  used  this  solvent  for  freezing-point  determinations,  but  did 
not  encounter  this  difficulty.23 

Ethylene  chlorobromide  was  made  according  to  Simpson's24  method  by 

21  Ref.  17,  p.  1662. 

22  Schneider,  Z.  physik.  Chem.,  22,  232  (1897). 

23  Beckmann,  Z.  anorg.  Chem.,  67,  31  (1910). 

24  Simpson,  Proc.  Roy.  Soc.,  27,  118  (1878).     Delepine  and  Ville,  Bull.  Soc.  Chim., 
[4]  27,  673  (1920). 


13 


passing  ethylene  into  a  mixture  of  chlorine,  bromine  and  water.  The 
freezing-point  constant  was  determined  according  to  the  method  described 
for  carbon  tetrachloride,  using  triphenylmethane  and  benzophenone. 
Since  the  values  obtained  in  this  case  were  constant,  the  average  of  the 
determinations  was  used.  Ethylene  chlorobromide  possesses  unusual 
advantages  as  a  cryoscopic  solvent.  It  has  a  high  constant  and  super- 
cools only  very  slightly.  As  far  as  we  know,  it  is  the  only  suitable  solvent 
freezing  at  or  near  — 17°. 

The  determinations  of  the  molecular  weight  of  the  free  radical  were 
carried  out  in  an  atmosphere  of  hydrogen.  Three  additions  were  made  and 
the  resulting  concentrations  were  from  1%  to  5%.  The  samples  were 
all  dried  under  reduced  pressure  in  an  atmosphere  of  carbon  dioxide.  In 
no  case  was  the  same  sample  used  for  two  determinations,  but  new  material, 
prepared  on  the  day  the  determination  was  made,  was  used  each  time. 
The  following  solvents  were  used:  carbon  tetrachloride,  ethylene  chloro- 
bromide, benzene,  nitrobenzene,  cyclohexane,  ^-bromotoluene,  ^-dichloro- 
benzene  and  naphthalene.  In  the  experiments  using  naphthalene,  where 
it  was  possible  that  the  high  temperature  might  produce  decomposition, 
repeated  determinations  showed  that  the  freezing  point  remained  per- 
fectly constant  and,  therefore,  the  conclusion  is  justified  that  no  decompo- 
sition was  taking  place. 

TABLE  IV 


Solvent 

CCU 

M.  p.-22' 


C2H4ClBr 
M.  p,-17° 


C6H6 

M.  p.  5.3° 


C6H5N02 

M.  p.  5.7° 


MOLECULAR  WEIGHT 

Constant 
K 

Weight  of 
solvent 

Weight  of 
solute 

Concen- 
tration 

Depres- 
sion 

Molec- 
ular wt. 

Disso- 
ciation 

G. 

G. 

% 

°C. 

% 

348 

25.41 

0.4620 

1.84 

1.284 

498 

17.7 

333 

1  .0567 

4.20 

2.785 

503 

61.5 

324 

1.4716 

5.86 

3.673 

518 

13.1 

345 

25.44 

0.5614 

2.21 

1.588 

580 

21.8 

335 

0.9963 

3.92 

2.606 

503 

16.5 

321 

1.5700 

6.17 

3.978 

501 

16.9 

86.3 

25.03 

0.5349 

2.14 

0.393 

469 

25.0 

0.9527 

3.81 

0.695 

471 

24.4 

1.2783 

5.11 

0.916 

480 

22.1 

25.08 

0.4627 

1.70 

0.342 

464 

26.3 

0.9450 

3.77 

0.676 

480 

22.1 

1  .2533 

5.01 

0.896 

481 

21.8 

52.0 

17.69 

0.3697 

2.09 

0.248 

438 

33.8 

0.6612 

3.74 

0.430 

452 

29.6 

1.1352 

6.42 

0.720 

463 

27.2 

20.05 

0.3447 

1.72 

0.201 

443 

32.3 

0.5704 

2.85 

0.337 

442 

32.6 

0.9163 

4.57 

0.540 

461 

27.1 

69.0 

20.06 

0.4028 

2.01 

0.316 

438 

33.8 

0.7298 

3.64 

0.573 

438 

33.8 

0.9735 

4.95 

0.779 

439 

33.5 

14 


C6H12 

M.  p.  5.8° 


CH3C6H4Br 
M.  p.  27° 


C6H4C12 
M.  p.  53° 


C10H8 
M.  p.  80' 


20.10        0.3597         1 

.79 

0.280        441         32.9 

0.7425        3 

.69 

0.571         446         31.4 

0.9772        4 

.86 

0.762        440        33.2 

200            20.05        0.4855        2 

.42 

0.972        498         17.7 

0.7828        3 

.90 

1.482        527         11.2 

0.9824        4 

.90 

1.735      "565          3.7 

20.02         0.4271         2 

.13 

0.908        481         21.8 

0.7191         3 

.59 

1.388        518         13.1 

1.0211         5 

.1 

1.832        557          5.2 

85.5        27.66        0.4879         1 

.76 

0.333        451         30.6 

0.9900        3 

.58 

0.668        456        28.5 

1.4848        5 

.37 

0.988        462        26.8 

.  27.41         0.5239         1 

.91 

0.365        445        32.1 

1.0770        3 

.93 

0.740        451         30.0 

1.5160        5 

.53 

1.024        459        27.7 

72.2        24.91         0.5223        2 

.10 

0.342        444        32.0 

1.0577        4.25 

0.682        451         30.0 

1.5200        6 

.10 

0.974        454        29.1 

25.11         0.4940         1 

.97 

0.330        431         36.0 

0.9472        3 

.77 

0.604        451         30.0 

1.4246         5 

.86 

0.914        448        30.8 

71             19.97        0.5615        2 

.81 

0.515        388        51.0 

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1.029        408        43.6 

19.50        0.5381         2 

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0.499        391         49.9 

0.9548        4 

.90 

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The  Quantitative  Determination  of  the  Number  of  Decolorizations 
Produced  by  the  Action  of  Oxygen  on  Solutions  of  Diphenyl-j8-Naph- 
thylmethyl. — The  fact  that  solutions  of  free  radicals  are  decolorized  by 


15 

shaking  with  oxygen  and  that  the  color  reappears  upon  standing  has  been 
referred  to  in  the  introductory  part  of  this  paper.  The  approximate 
number  of  such  decolorizations  has  been  determined  by  several  investi- 
gators.25 We  found  that  such  results  varied  greatly  with  the  conditions 
of  the  experiment.  Therefore,  a  definite  procedure  was  adopted  and  an 
apparatus  was  devised  for  the  investigation  of  this  phenomenon.  The 
apparatus  was  quite  similar  to  the  usual  form  of  absorption  apparatus 
which  has  already  been  described,  except  that  the  absorption  vessel  was 
replaced  by  a  lOOcc.  Nessler  tube.  This  tube  was  tightly  stoppered  and 
provided  with  a  fairly  close  fitting  cork  piston  which  was  moved  by  an 
iron  rod  passing  through  the  stopper.  In  order  to  make  a  gas-tight 
joint,  yet  one  through  which  the  rod  would  slide  easily,  an  iron  tube  slightly 
larger  than  the  rod  was  inserted  in  the  stopper  and  a  rubber  tube  was 
fitted  tightly  over  both  the  iron  sleeve  and  the  rod.  By  the  use  of  a  little 
glycerine  this  joint  was  made  perfectly  gas  tight  and  yet  it  did  not  hinder 
the  free  motion  of  the  piston.  A  tube  connecting  with  the  gas  buret 
was  also  inserted  through  the  rubber  stopper. 

For  the  determination,  a  Ig.  sample  of  the  free  radical  was  placed  in 
a  test-tube  of  15cc.  capacity,  sufficient  bromobenzene  was  added  to  fill 
the  tube,  and  the  tube  was  sealed.  The  substance  was  quickly  dissolved 
by  shaking.  The  tube  was  then  placed  in  the  Nessler  tube  just  described, 
enough  bromobenzene  was  added  to  make  a  total  volume  of  50  cc.  and  the 
tube  was  connected  with  the  buret  of  the  absorption  apparatus.  The 
apparatus  was  exhausted  and  filled  with  oxygen.  The  test-tube  was  broken 
by  pressing  down  the  p'ston,  which  was  adjusted  so  that  its  under  surface 
was  in  contact  with  the  surface  of  the  liquid,  thus  sealing  the  solution  al- 
most completely  from  the  oxygen  above.  The  liquid  in  the  gas  buret 
was  leveled  and  the  reading  was  taken.  The  piston  was  then  withdrawn 
as  far  as  possible  in  order  to  admit  a  fresh  supply  of  oxygen  and  the  solution 
was  shaken  for  a  few  seconds  until  the  color  of  the  free  radical  disappeared. 
The  piston  was  then  quickly  pushed  in  and  the  absorption  was  determined. 
The  same  procedure  was  repeated  at  2-minute  intervals.  After  the  last 
easily  perceptible  color  change  had  taken  place,  the  tube  was  shaken 
vigorously  until  no  more  absorption  of  oxygen  occurred.  The  last  reading 
represents  not  merely  the  oxygen  required  to  produce  perceptible  decolori- 
zation  but  the  amount  necessary  to  complete  entirely  the  oxidation  of  the 
free  radical.  The  values  for  the  percentage  of  oxygen  absorbed  at  each 
interval  are  based,  not  on  the  amount  which  would  be  required  by 
theory  for  the  entire  oxidation,  but  on  the  actual  amount  of  oxygen 
which  was  absorbed  in  the  experiment  under  consideration.  This  hap- 

25  Schmidlin,  Ber.,  41,  2476  (1908).  Schlenk  and  Weickel,  Ann.,  372,  7  (1909). 
Schlenk  and  Renning,  ibid.,  394,  194  (1912).  Schmidlin  and  Garcia-Banus,  Ber.,  45, 
3186  (1912). 


16 


pened  to   be   somewhat  less  than  that  calculated  for  the   amount  of 
free  radical  taken. 

TABLE  V 
DECOLORIZATION  BY  OXYGEN 


Sample  I 

Weight  of  sample,  1.000  g. 
Solvent,  50  cc.  of  C6H6Br 
Temp.,  21°.     Bar.,  744  mm. 
%  of  calc.  absorption,  87.3 

Oxygen0 

Total0          abs.  for     % 
oxygen  ab-       single  absorp- 

sorption  decolorization      tion 


Interval 

sorpti< 

1 

5.1 

2 

9.2 

3 

12.9 

4 

16.9 

5 

19.6 

6 

22.3 

7 

23.8 

8 

25.6 

9 

26.7 

10 

28.0 

Total 

34.5 

Sample  II 

Weight  of  sample,  1.000  g. 
Solvent,  50  cc.  of  C6H5Br 
Temp.,  22°.     Bar.,  730  mm. 
%  of  calc.  absorption,  96.7 

Oxygen0 

Total0  abs.  for       %  of  total 

oxygen  single  absorp- 

absorption  decolorization      tion 


5.1 

14.9 

4.1 

26.7 

3.7 

37.5 

4.0 

49.0 

2.7 

56.9 

2.7 

64.7 

1.5 

68.9 

1.8 

74.2 

1.1 

77.3 

1.3 

81.2 

6.5 

100 

5.2 
8.9 
13.2 
17.3 
19.9 
22.6 
25.3 
27.6 
29.2 
30.8 
37 


5.2 
3.7 
4.3 
3.9 
2.6 
2.7 
2.7 
2.3 
1.6 
1.6 
6.2 


13.9 
24.0 
35.6 
64.9 
53.9 
61.1 
68.3 
74.5 
78.9 
83.2 
100 


Corrected  to  standard  conditions. 


Similar  experiments  were  conducted  with  triphenylmethyl  and  di- 
phenyl-a-naphthylmethyl  but  the  turbidity  produced  by  the  immediate 
precipitation  of  the  peroxide  obscured  the  end-point.  Twelve  clearly  dis- 
tinguishable changes  were  observed  with  the  former  and  only  three  with 
the  latter.  Such  a  method  as  here  employed  is  suited  for  use  only  with 
compounds  which  show  a  decided  color  change  on  oxidation  and  which  give 
a  clear  solution  by  virtue  of  the  solubility  of  the  corresponding  peroxide, 
as  happened  to  be  the  case  with  diphenyl-/3-naphthylmethyl. 

Colorimeter  for  the  Study  of  the  Changes  in  Intensity  of  Color  of 
Solutions  of  Free  Radicals. — For  the  quantitative  determination  of  the 
color  of  a  free  radical  solution  of  a  Campbell-Hurley  colorimeter26  was 
used,  with  such  changes  as  were  necessary  in  order  to  work  in  the  absence 
of  oxygen. 

The  tube,  B,  which  was  to  contain  the  solution  under  investigation  was  fitted  with  a 
glass  plate  sealed  to  the  top  and  with  2  side-arms  placed  near  the  top.  The  lower  side- 
arm  was  fitted  with  a  ground-glass  joint  to  which  was  attached  a  3-way  stopcock,  a. 
One  opening  of  the  stopcock  connected  with  a  funnel  for  the  introduction  of  solvent  while 
the  other  led  to  the  carbon  dioxide  generator.  The  upper  side-arm  was  connected 
through  a  stopcock,  b,  to  the  suction  pump.  The  other  colorimeter  tube,  A,  which  was 
to  contain  the  standard  solution,  was  also  sealed  with  a  plate  at  the  top  and  fitted  with 
2  side-arms,  one  as  near  the  bottom  as  possible  and  the  other  near  the  top.  The 

26  Campbell  and  Hurley,  J.  Am.  Chem.  Soc.,  33,  1112  (1911). 


17 

lower  arm  was  connected  by  a  ground-glass  joint  to  a  tube  leading  to  the  Drechsel  bottle, 
C,  which  served  as  a  reservoir  for  the  standard  solution.  To  the  other  arm  of  the 
Drechsel  bottle  was  fused  a  3-way  stopcock,  c,  one  arm  of  which  connected  with  the  suc- 
tion pump  and  the  other  with  the  carbon  dioxide  generator.  This  arm  of  the  Drechsel 
bottle  was  attached  also  to  a  second  3-way  stopcock,  d,  one  outlet  of  which  connected 
with  the  funnel  for  the  introduction  of  solvent  and  the  other  led  back  to  the  upper  side- 
arm  of  the  colorimeter.  This  upper  side-arm  was  also  fitted  with  a  2-way  stopcock,  e, 
and  trap  for  the  outlet  of  carbon  dioxide.  The  carbon  dioxide  for  these  experiments 
was  freed  from  all  traces  of  oxygen  by  passing  over  reduced  copper  at  a  dull  red  heat. 

To  prepare  the  standard  solution,  0 . 5  g.  of  the  free  radical  was  placed 
in  the  Drechsel  bottle,  C.  The  apparatus  was  evacuated,  filled  with  car- 
bon dioxide  and  100  cc.  of  benzene  was  added.  The  free  radical  dissolved 


Fig.  5. 

rapidly.  The  apparatus  was  kept  under  a  positive  pressure  of  carbon 
dioxide  all  the  time.  To  raise  the  column  in  the  colorimeter  tube,  the 
stopcock  d  was  closed  and  the  stopcock  e  was  opened.  The  pressure 
forced  the  solution  into  the  colorimeter  tube.  To  empty  the  colorimeter 
tube  the  stopcock  d  was  opened  and  e  was  closed.  By  repeating  this 
procedure  a  few  times,  the  solute  was  completely  dissolved  and  the  solution 
was  well  mixed.  The  reliability  of  the  apparatus  was  thoroughly  tested. 
A  solution  in  B  when  made  up  to  the  same  strength  as  the  standard  in  A 


18 


and  compared  with  it  was  invariably  balanced  exactly  by  a  column  of 
the  standard  solution  of  the  same  height. 

The  Effect  of  Dilution  on  the  Color  of  Solutions  of  Free  Radical  in 
Benzene,  Nitrobenzene  and  Cyclohexane  at  their  Respective  Freezing 
Points. — One-quarter  g.  of  the  free  radical  was  dissolved  in  5  cc.  of  solvent 
in  the  colorimeter  tube  B.  The  solution  was  frozen  by  immersing  in  a 
cooling  mixture  and  then  allowed  to  melt  until  a  few  crystals  remained. 
It  was  then  compared  with  the  standard  in  A  and  5  readings  were  taken. 
Readings  were  easily  duplicated  within  1  mm.  The  solution  was  then  di- 
luted by  the  addition  of  5  cc.  of  solvent,  frozen  and  compared  with  the 
standard  again.  Finally  it  was  diluted  to  25  cc.  This  procedure  was 
carried  out  with  each  of  the  3  solvents.  The  experiments  were  carried 
out  in  duplicate  on  solutions  made  by  dissolving  different  samples  of  free 
radicals,  but  since  the  two  experiments  checked  exactly  only  one  is  reported. 

TABLE  VI 
CHANGE  OF  COLOR  WITH  DILUTION 


Read- 
ings 

Volume 
soln. 

Nitrobenzene 
%  Cone.     Height 
by  wt.      standard 

Benzene 
%  Cone.        Height 
by  wt.       standard. 

Cyclohexane 
%  Cone.     Height 
by  wt.      standard. 

Cc. 

Mm. 

Mm. 

Mm. 

1 

5 

4.15 

13 

5.68 

11.5 

6.85 

10 

2 

10 

2.08 

17 

2.84 

16 

3.43 

14 

3 

25 

.83 

25 

1.14 

23 

1.37 

19 

The  Effect  of  Temperature  on  the  Color  of  Solutions  of  the  Free 
Radical  in  Carbon  Tetrachloride  and  in  Toluene. — A  solution  containing 
2  g.  of  the  free  radical  per  100  cc.  of  carbon  tetrachloride  was  frozen  in 
a  mixture  of  carbon  dioxide  and  toluene.  The  color  at  the  freezing  point 
was  compared  with  that  of  the  standard  solution  at  room  temperature. 
A  number  of  comparisons  were  made  throughout  a  temperature  range  from 
the  freezing  point  of  carbon  tetrachloride,  — 22°,  to  +30°.  Similar  com- 

TABLE  VII 
CHANGE  OF  COLOR  WITH  TEMPERATURE 

Height  of  solution,  17  mm. 
Temp.  CC14'         Height  stand.        Temp.  C7H{ 
°C.  Mm.  °c. 

-39 
-26 


-22 
-15 


10 
20 

30 


6 


15 

23 
33 

50 


-18 

-10 

-5 

0 

5 

12 

20 

25 

30 


Height  stand. 
Mm. 

3 

4 

6. 

9 
11 
13 

17.5 
20.5 
28 
36 
41 


19 

parisons  were  made  upon  a  2%  toluene  solution  at  various  temperatures, 
from  the  freezing  point  of  mercury,  — 39°,  to  -+-30°.  The  standard  so- 
lution for  these  comparisons  was,  as  before,  a  0.5%  solution  of  the  free 
radical  in  benzene. 

The  fact  that  the  color  of  the  free  radical  solution  upon  cooling  does  not 
decrease  beyond  a  certain  limit,  may  be  due  to  the  presence  of  colored  im- 
purities. This  suspicion  is  strengthened  by  the  fact  that  the  solid  free 
radical  itself  is  colored  slightly.  If  this  surmise  be  correct,  then  the  read- 
ings given  are  all  somewhat  too  high  and  should  be  corrected  by  subtracting 
the  value  of  the  least  reading,  3  mm.  We  were  unable  to  obtain  a  solution 
of  the  free  radical  in  carbon  tetrachloride  or  toluene  whose  color  disap- 
peared entirely  even  when  cooled  to  the  lowest  temperature  obtainable 
with  a  mixture  of  carbon  dioxide  and  toluene. 

Discussion  of  Results 

Diphenyl-/3-naphthylmethyl  is  a  pure  white  substance  which  rapidly 
becomes  yellow  on  standing,  even  in  an  atmosphere  of  carbon  dioxide. 
In  contrast  to  its  a-naphthyl  isomer,  it  is  very  soluble  in  all  the  common 
solvents  and  crystallizes  only  on  long  standing. 

It  absorbs  the  theoretical  amount  of  oxygen  to  form  the  peroxide  but 
does  not  give  a  high  yield  of  the  crystalline  substance.  The  free  radical 
is  quickly  decomposed  by  hydrogen  chloride  and  slowly  acted  on  by  light. 

The  equilibrium  between  the  free  radical  and  iodine  is  reached  when  70% 
of  the  theoretical  amount  of  iodine  has  been  added.  The  concentrations 
of  the  products  present  when  equilibrium  has  been  reached  are  inter- 
mediate between  those  in  the  case  of  triphenylmethyl  and  in  the  case  of 
diphenyl-a-naphthylmethyl. 

The  results  of  the  conductivity  determinations  show  that  the  property 
of  electrolytic  dissociation  is  a  general  one  for  this  class  of  compounds. 
The  bromides  give  strongly  conducting  solutions  with  but  little  difference 
between  the  conductivities  of  the  individuals.  The  chlorides  are  not 
such  good  conductors  and  there  is  a  variation  among  them.  The  con- 
ductivities of  the  chlorides  are  related  in  the  same  way  as  the  dissociation 
of  the  corresponding  free  radicals;  the  chloride  of  diphenyl-a-naphthyl- 
methyl, highest;  of  diphenyl-/3-naphthylmethyl,  next;  and  of  triphenyl- 
methyl, least.  Triphenylmethyl  chloride  has  a  large  negative  temperature 
coefficient  of  conductivity.  The  same  relation  holds  for  the  free  radicals 
themselves;  diphenyl-£-naphthylmethyl  is  a  better  conductor  than  tri- 
phenylmethyl. 

The  conductivity  of  the  triarylmethyl  halides  in  hydrocyanic  acid  is 
uniformly  higher  than  in  sulfur  dioxide.  The  bromides  show  molecular 
conductivities  comparable  to  that  of  an  aqueous  solution  of  potassium 
hydroxide  or  about  twice  the  conductivity  of  the  alkali  halides  in  water. 


20 

This  is  a  striking  fact,  in  view  of  the  high  molecular  weight,  373,  the  great 
complexity  of  the  molecules,  and  in  view  of  the  absence  of  any  basic 
groups  like  the  amino  group.  The  chlorides  conduct  less  than  the  corre- 
sponding bromides  and  the  individual  variations  are  the  same  as  those  ob- 
served for  the  same  substances  in  sulfur  dioxide. 

The  colors  of  the  solutions  of  the  free  radicals  in  sulfur  dioxide  are: 
triphenylmethyl,  orange  yellow;  diphenyl-a-naphthylmethyl,  green; 
diphenyl-/3-naphthylmethyl,  red.  The  halides  of  these  free  radicals  give 
the  same  colors  when  dissolved  in  sulfur  dioxide,  hydrogen  cyanide 
or  sulfuric  acid.  The  color  is  very  intense  and  a  minute  quantity  of  sub- 
stance suffices  to  impart  a  deep  color  to  a  large  volume  of  solvent.  Merely 
from  a  visual  comparison  of  the  solutions  of  diphenyl-/3-naphthylmethyl 
or  of  its  halogen  derivatives  in  sulfur  dioxide  with  a  benzene  solution  of  the 
free  radical  itself,  it  is  evident  that  the  phenomenon  of  electrolytic  dissoci- 
ation with  the  accompanying  color  is  entirely  different  from  the  phenomena 
of  dissociation  and  color  formation  of  the  free  radical  which  takes  place 
in  non-dissociating  solvents.  Also,  the  same  difference  is  apparent  when 
the  bright  green  sulfur  dioxide  solutions  of  the  a-naphthyl  derivatives 
are  compared  with  the  dark  brown  solution  of  this  free  radical  in  benzene. 
Kurt  H.  Meyer  and  H.  Wieland27  had  previously  come  to  a  similar  con- 
clusion in  regard  to  triphenylmethyl  and  its  derivatives.  As  a  result  of 
spectroscopic  investigations,  they  found  that  the  colors  of  triphenylmethyl 
solutions  in  sulfur  dioxide  and  in  benzene,  while  apparently  identical,  in 
reality  were  distinctly  different. 

As  a  result  of  previous  molecular  weight  determinations  upon  a  number 
of  free  radicals  certain  generalizations  have  been  drawn  concerning  their 
dissociation.  Diphenyl-/3-naphthylmethyl  conforms  to  the  generaliza- 
tion that  dissociation  increases  with  dilution  except  in  a  few  cases  where 
deviations  can  be  attributed  to  experimental  errors. 

The  results  of  the  determinations  of  the  molecular  weight  of  triphenyl- 
methyl indicate  that,  within  certain  limits,  the  dissociation  of  hexaphenyl 
ethane  is  proportional  to  the  temperature  of  the  solution  and  independent 
of  the  nature  of  the  solvent.  This  hypothesis  was  borne  out  by  subse- 
quent work  on  diphenyl-a-naphthylmethyl  which  showed  a  very  regular 
increase  in  dissociation  with  increase  in  temperature,  quite  independent 
of  the  nature  of  the  solvent.  In  a  set  of  experiments  upon  the  j8-naph- 
thyl  free  radical,  performed  to  test  this  point,  using  nitrobenzene,  benzene 
and  cyclohexane,  it  was  found  that  there  are  exceptions  to  this  rule.  The 
solvents  all  possess  approximately  the  same  freezing  points,  5°  to  6°. 
In  nitrobenzene  and  benzene,  the  molecular  weights  are  practically  the 
same.  In  cyclohexane,  however,  the  molecular  weight  of  the  free  radical 
is  very  high  and  increases  rapidly  with  concentration  until,  in  a  5%  solu- 

27  Meyer  and  Wieland,  Ber.,  44,  2557  (1911). 


21 

tion,  it  is  almost  completely  associated.  This  peculiar  behavior  is  in  har- 
mony with  the  observations  of  Mascarelli  and  Benati28  who  found  that, 
as  compared  with  the  ordinary  cryoscopic  solvents,  cyclohexane  was  very 
strongly  associating.  It  might  be  expected  that  a  solvent  possessing  this 
tendency  would  certainly  exhibit  it  toward  a  free  radical.  The  accom- 
panying graph  shows  that,  in  general,  dissociation  increases  with  temper- 
ature. 

The  results  of  the  experiments  on  the  relation  between  dissociation  and 
the  oxygen  necessary  to  produce  decolorization  proves  conclusively  that 
the  color  is  not  proportional  to  the  dissociation.  A  2%  solution  of  the 
hexa-aryl  ethane  in  ^-bromotoluene  at  its  freezing  point  is  about  30% 
dissociated.  A  bromobenzene  solution  of  the  same  concentration  at  the 


same  temperature  is  completely  decolorized  by  only  14%  of  the  oxygen 
necessary  for  complete  oxidation.  How  are  we  to  explain  the  fact  that 
the  decolorization  is  produced  by  only  x/2  of  the  oxygen  which  would  be 
necessary  to  oxidize  the  whole  amount  of  the  monomolecular  form  present 
in  solution?  Evidently  only  on  the  assumption  that  the  monomolecular 
form  exists  as  two  tautomers,  one  of  which  is  colored  and  which  reacts 
more  rapidly  with  oxygen  than  the  colorless  form.  Of  course,  the  results 
obtained  by  decolorization  cannot  be  assumed  to  represent  the  true  amount 
of  the  colored  tautomer,  first,  because  the  colorless  form  may  also  be  ab- 
sorbing some  oxygen  and,  second,  because  the  colorless  form  undoubtedly 
tautomerizes  partly  into  the  colored  form  during  the  process  of  decolori- 
zation. The  values  do  certainly  represent  the  maximum  possible  amount 
of  the  colored  tautomer  in  the  solution.  These  results  differ  from  Schmid- 
lin's  on  triphenylmethyl  in  that  the  decolorization  experiments  here 
described  are  paralleled  by  a  series  of  accurate  molecular-weight  deter- 
minations on  a  substance  of  appreciable  dissociation,  and  we  are  therefore 
28  Mascarelli  and  Benati,  Gazz.  chim.  ital,  39,  [2]  642  (1909). 


22 


in  a  position  actually  to  correlate  intensification  of  color  with  increase  of 
dissociation. 

It  was  found  that  solutions  of  the  free  radicals  in  cyclohexane,  benzene 
and  nitrobenzene  are  of  about  the  same  intensity  of  color  and  that  the 
intensity  of  color  changes  equally  in  all  cases  on  dilution,  in  spite  of  the 
differences  in  dissociation  in  these  solvents.  Assuming  the  color  of  a 
5%  solution  to  be  unity,  we  can  calculate  the  relative  intensity  of  color 
at  dilutions  down  to  1%  in  ref- 
erence to  this  unit.  Plotting 
these  color  values  against  the 
dilution,  that  is,  the  number  of 
grams  of  solvent  containing  1 
g.  of  solute,  we  obtain  curves 
a,  6,  c,  (Fig.  7),  showing  the 
relative  change  of  color  inten- 
sity with  dilution.  Similarly, 
we  assume  the  degree  of  disso- 
ciation at  5%  as  our  unit  and 
calculate  the  relative  degree  of 
dissociation  at  other  dilutions 
with  reference  to  this  unit. 
These  values  are  also  plotted 
against  the  dilution,  and  the 
resulting  curves  a',  bf,  c',  show 
the  relative  change  in  dissocia- 
tion on  dilution.  It  is  appar- 
ent, in  nitrobenzene  and  ben- 


D/L unfit  *cc. 

COLOR  //v 


0/ss'w  //v 


zene  the  intensity  of  color  al- 
most doubles  with  the  decrease 
of  concentration  from  5%  to 
1%  and  yet  the  change  in  dis- 
sociation throughout  the  same 
range  is  very  slight.  On  the 
other  hand  in  cyclohexane,  the 
dissociation  increases  three  times  as  much  as  the  color.  This  again  shows 
that  color  is  independent  of  dissociation,  that  is,  an  increase  in  dissocia- 
tion may  occur  without  an  equal  increase  in  color  intensity. 

It  was  found  that  a  solution  of  the  free  radical  in  carbon  tetrachloride 
at  its  freezing  point,  or  in  toluene  at  — 40°,  is  only  slightly  colored  although 
it  is  dissociated  to  the  extent  of  from  15  to  20%.  On  gradually  warming 
these  very  light  colored  solutions,  an  increase  in  color  begins  to  take  place 
between  — 30°  and  — 20°  and  this  color  increases  10  times  with  a  rise  of 
temperature  of  50°  while  the  dissociation  increases  only  l/2  with  the  same 


23 

change  of  temperature.  If  we  assume  as  the  unit  of  color  intensity  the 
color  of  a  solution  at  — 20°  and  calculate  the  relative  color  intensity  at 
other  temperatures  with  reference  to  this  unit,  then  plot  these  values 
against  the  temperature,  we  obtain  curves  a,  b,  (Fig.  8),  showing  the  relative 
increase  of  color  with  temperature.  If  we  now  take  as  our  unit  of  dis- 
sociation the  amount  of  dissociation  at  — 20  °  we  can  calculate  the  relative 
dissociation  at  other  temperatures  with  reference  to  this  unit.  Plotting 
these  values  against  the  temperature  we  obtain  a  curve,  c,  showing  the 
increase  of  dissociation  with  rise  of  temperature.  The  accompanying 
curves  show  the  striking  differences  between  the  change  in  the  degree 
of  dissociation  and  the  change  in  color  intensity  which  occurs  when  the  tem- 
perature of  the  solution  of  the  free  radical  is  varied. 


D/SSN*  C, 


It  is  not  our  purpose  to  explain  in  what  manner  the  effect  of  dilution, 
or  that  of  rising  temperature,  operates  to  disturb  the  equilibrium  between 
the  colored  and  colorless  modifications  of  the  free  radical.  However, 
our  results  do  definitely  prove  that  changes  in  color  intensity  take  place 
independently  of  changes  in  dissociation.  The  evidence  presented  is 
convincing.  This  being  M>,  then  the  observed  facts  can  best  be  explained 
by  the  assumption  that  we  are  dealing  here  with  an  equilibrium  between 
benzenoid  and  quinonoid  tautomers  of  the  triaryl  methyl,29  and  that  an 
increase  in  the  proportion  of  the  quinonoid  tautomer  is  the  cause  of  the  in- 
crease of  color. 

Summary 

'  1.     Diphenyl-0-naphthyl   carbinol    has   been    synthesized  from  ethyl 
/3-naphthoate    and    phenylmagnesium    bromide.     A    number    of   its    de- 
*»Cf.  P.  1811. 


24 

rivatives  were  prepared.  Diphenyl-/3-naphthylmethyl  chloride  was 
obtained  by  the  action  of  hydrogen  chloride  on  the  carbinol.  When 
the  chloride  was  treated  with  molecular  silver,  the  free  radical,  diphenyl- 
/3-naphthylmethyl,  resulted. 

2.  The  radical  was  isolated  in  the  crystalline  state.     A  careful  study 
was  made  of  its  reactions  with  oxygen,  iodine  and  acids,  and  of  the  effect 
of   light.     The   conductivity   of   the   free   radical,    diphenyl-/3-naphthyl- 
methyl,   was  determined  in  sulfur  dioxide.     The  conductivities  of  the 
chlorides  and  bromides  of   triphenylmethyl,  diphenyl-a-naphthylmethyl 
and  diphenyl-/3-naphthylmethyl  were   determined  in  both  sulfur  dioxide 
and  hydrogen  cyanide.     These  compounds,  especially  the  bromides,  were 
found  to  be  good  conductors.     The  molecular  weight  of   diphenyl-/3- 
naphthylmethyl  was  determined  in  8  solvents  whose  freezing  points  covered 
the  range  from  — 22  °  to  +  80  °.      It  was  found  that  the  hexa-arylethane  was 
dissociated  from  15%  to  50%. 

3.  Experiments  were  carried  out  to  find  what  effect  changes  in  con- 
centration of  the  free  radical  would  have  upon  the  dissociation  and  upon 
the  color  of  the  solutions.     It  has  been  found  that  the  resulting  changes 
in  color  intensity  are  independent  of  the  changes  in  dissociation.     It  has 
also  been  found  that  the  changes  in  color  intensity  which  result  from  vari- 
ations in  temperature  are,  again,  not  parallel  to  the  changes  in  dissociation 
which  are  thus  produced.     These  facts  point  to  the  conclusion  that  color 
formation  in  solutions  of  free  radicals  is  not  due  wholly  to  dissociation  of 
the  hexa-aryl  ethane  into  the  tri-aryl  methyl.     The  most  satisfactory 
explanation  of  the  facts  is  the  hypothesis  that  in  addition  to  dissociation 
we  have  tautomerization  of  the  benzenoid  tri-arylmethyl  into  the  quin- 
onoid  form.       The  equilibrium  between  the  dimolecular  and  monomolec- 
cular  forms  on  the  one  hand  and  the  equilibrium  between  the  two  mono- 
molecular  tautomers  on  the  other  hand,  are  not  equally  influenced  by 
changes  either  in  concentration  or  in  temperature. 

This  investigation  was  made  with  the  assistance  of  The  National  Ani- 
line and  Chemical  Company  Fellowship,  and  we  wish  to  express  our  ob- 
ligations for  the  generous  aid  we  have  thus  received. 


BOOK 

a 


MOV   6     1932 


MOV 


1932, 


•^ 


LD  2i_« 


•32 


507573 


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